Instacart Software Engineer Interview Experience — Two Coding Rounds, a Manager BQ Chat, and a System Design Round

Two rounds of coding, and both were problems that had already been posted elsewhere before. The first one: the input is a transaction record and a set of discounts, and the discounts come in two types — one is a straight percentage off, the other is buy x get y free. The result you need to return is the best (lowest) price. There were 3 parts total, and I only got through the second part before time ran out — never even started the third.

The second question had also been posted by someone else before. The input has two parameters. The first gives you T1 equals something, T2 equals something, where the right side of the equals sign could be a number or could be another variable. The second input parameter is the var you need to evaluate. Not hard — you just do it with recursion until you find the final result. After I finished, they asked about time complexity, and how I'd improve it if it needed to meet production code standards.

Overall the coding rounds weren't hard.

The third round was BQ, where an engineering manager chats with you. They asked about projects I'd led in past jobs, and asked about technical tradeoffs and details.

The fourth round was system design. Also a classic inventory problem — design a simplified version of Instacart's system. No need to think about the frontend. Other posts have also written up the specifics of this one.

Two days after the interview I was told I didn't get it. My own sense is that the round I did worst on was the manager chat — I feel like my experience from my last job worked against me there. Even while I was still at that job I already felt the project was pretty niche and had no standout points, and while the manager was listening he said "interesting" several times, which felt like a mix of not quite getting it but still listening to me keep going. Beyond feeling like I didn't answer well, the project itself from my last job was probably something of a minus too.

Job hunting feels so hard right now... guess I need to get into the mindset of being unemployed long-term~